1. Field of Invention
The present invention relates to microelectronics; and more particularly, to a microelectrostatic voltage controlled cantilever switch.
2. Discussion of Related Art
Microelectrostatic voltage controlled switches are used to conduct RF current in applications that involve the of antenna phase shifters, and RF shutters for the protection of radar arrays, for example. Typically these switches comprise a conductive cantilevered beam mounted on a silicon substrate wherein the cantilevered beam has an unsupported portion or free end that overhangs a contact pad. When in an open position, the free end of the cantilevered beam is spaced from the gold contact pad. In response to a DC pull-down voltage applied to the pull down electrode, the substrate coulomb forces cause the free end of the cantilevered beam to engage the surface of the contact pad, thus, resulting in the flow of current from the cantilevered beam to the contact pad.
It has been found that these switches are capable of conducting RF current through approximately ten million switching cycles without failure. After operating in excess of the approximately ten million cycles, the free end of the cantilevered beam tends to stick to the contact pad, which at best decreases the opening speed of the switch, and at the worst causes the switch to remain in its closed position.
Although ten million switching cycles without failure is acceptable for many switching applications, this failure is unacceptable for uses where reliability is paramount over periods of time, such as applications in outer space, for example.
In light of the foregoing, there is a need for microelectrostatic voltage controlled switches that are able to be manufactured at a cost commensurate with and operate effectively as those heretofore developed, but which are also without failure for a substantially greater number of switching cycles.